What is the best way to prepare the metal for painting after soda blasting? - Ford Mustang Forum
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post #1 of 5 (permalink) Old 02-14-2010 Thread Starter
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Smile What is the best way to prepare the metal for painting after soda blasting?

Hello, all!

Newbie here again. I am nearly complete in soda blasting the engine compartment on my Mustang. As anyone with soda blasting experience knows, soda blasting does not eliminate rust. It gets rid of the barnacles, but not the discoloration nor the active layer of rust (maybe there's a better way to express that?). I realize many of you will chastise me for my choice of soda blasting, but spare me - please! It's too late for that. Orbital sanding in the engine compartment is not my idea of a good time. Once I got a dessicant dryer and some practice, it moved along fairly well (you can actually peel away a single layer of paint at a time!).

Now I have exposed the metal and all the rust beneath the paint. My question is - how to treat the rust? I have been using "Evapo Rust" by the gallon for rust removal on parts, but it isn't a gel and it doesn't cling. Most things have to be soaked over night in Evapo Rust, then dipped in clean Evapo Rust and air dried (to prevent flash rusting). I also have "The Must for Rust" a spray on product that suggests it can be applied, allowed to dry, and painted over (I am skeptical about trying this on anything larger than a quarter).

What are the best practices for this? I have read about dilute vinegar washing, but that doesn't deal with the rust. In your response, please address all three parts - washing/neutralizing the soda, rust treatment/removal, and priming.

Thanks! I have read a number of postings and you guys/gals are very insightful!
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post #2 of 5 (permalink) Old 02-15-2010
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well most of the metal conditioners and metal cleaners act in the same way i use the Du Pont metal conditioner and acid wash but im sure what you have is pretty much the same. If you have the means to do so i prefer to actually sand blast with an 80 grit sand to remove rust. if there are any severe pits or holes weld accordingly or fill with liquid all metal (metal based body filler) then you have a choice of either epoxy primer or acid etch primer. the benefit of epoxy primer is you can lay down up to almost 2 mils of product so you can then scuff with 150 grit sand paper and repair any imperfections with body filler on top of the primer both primers can be primed over with a high build primer and top coated with either solvent based or water based paint. but in reference to your query on metal prep i would honestly just sand blast it.

this is just the way i do it. if there is an easier or more effective way out there my ears are open too and i would appreciate the info as well.
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post #3 of 5 (permalink) Old 02-15-2010
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I don't know about neutralizing the soda. You are right in that it's a fairly controversial issue but it is done and frequently. I do think there are some commercial products available for this but do not know what they are off the top of my head. Google will surely reveal some answers for you.

Regarding removal of rust from the engine bay, sometimes there is no easy way to do it and my weapon of choice is a wire wheel.

After you have removed all the rust and everything is down to bare metal, you need to degrease your metal well (this is the most critical step in paint prep) with a paint prep degreasing solvent, blow and tack the metal off, and then prime all the metal with a good ETCHING primer. The etching primer is essential as it will etch into the metal which not only makes a good surface for painting, but it seals the metal too and prevents rust from coming back.

The green stuff is the Sikkens Washprimer (etching primer) I used. It's expensive ($20 a can) but it's as professional top of the line that you can get. Normally the wash primer is a two part that's mixed together when spraying but they somehow figured out how to make an aerosal one too. The haze in final picture is literally paint haze.
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post #4 of 5 (permalink) Old 02-15-2010
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Soda has some issues as you know. Here is a wiki article on it: http://www.crankshaftcoalition.com/wiki/Soda_blasting

To neutralize soda you can:
  • Holdtight 102 has been recommended for use in cleaning soda-blasted surfaces prior to application of primer.
  • A vinegar and water solution is occasionally recommended, but has also been cautioned against.
  • Pressure washer and soap (Simple Green or Purple Power). While the car is wet, rinse with a hose. Do this at least 2-3 times. If any of the residue re-dries, water will not neutralize it, and it will have to be retreated.
  • Dish soap with warm water and a red scuff pad. Scrub panels and rinse with hose three times.
A very detailed article in Hotrodders on metal prep to remove rust prior to using epoxy paint. Epoxy is the preferred metal protector. secrets of surface rust removal revealed

Hope this helps

Good Luck and BE Safe

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Last edited by CathyHalliday; 04-01-2010 at 12:57 PM.
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post #5 of 5 (permalink) Old 02-16-2010 Thread Starter
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Thumbs up Thanks, guys!

Excellent posts! I appreciate the links to the previous postings. It's hard to sift through thousands of links to find the gems!
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metal prep , priming , rust , soda blasting

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